A torque tube conventionally comprises a body that is substantially cylindrical terminating at an inboard end in a radially depending mounting flange and at an outboard end in a radially extending backplate flange. The inboard mounting flange is characterized by a plurality of bolt retaining bores which function to affix the torque tube to a member of the wheel and brake assembly which is relatively stationary with respect to any rotating members of the assembly. The torque tube body is characterized by a plurality of axially oriented and longitudinally extending key surfaces which are adapted for engagement with alternating ones of a brake disk stack so as to maintain the disks stationary relative to disks which are rotating with a wheel.
The backplate flange functions to engage the brake disk stack through an end plate disk such that the disk stack is clamped between it and a brake pressure plate at the inboard end of the disk stack. The pressure plate is a disk which functions to accept axial load forces imposed on it by a plurality of hydraulically-operated pistons carried within a brake housing member and these are responsive to a call for wheel braking in a well-known and practiced manner.
A torque tube is conventionally a one-piece forged or cast steel or other suitable metal member which is machined to close tolerance to obtain the necessary keying interconnections with specific ones of the brake disk stack. Multiple machining operations are usually necessary to achieve such close tolerance and this, of course, increases the cost of the torque tube. Ways are being sought to decrease the number of machining operations and thus reduce the cost of these very necessary and important members of a wheel and brake assembly. In addition and because the backplate flange must accept and absorb the very high axial load forces imposed during braking of a rotating aircraft wheel, various configurations of backplate ribs have been developed into the outboard end so as to strengthen and stiffen the backplate flange. While such ribs are effective in achieving this, they also tend to add to the overall weight of the torque tube which works against recent efforts to decrease the weight. Furthermore, the various outboard configured strengthening ribs are limited in design by the volume space and axial extent available within a specific wheel which carries the brake assembly.
It is, therefore, in accordance with a primary aspect of the present invention an object to provide a disk brake torque tube having a configuration of backplate flange stiffening ribs which may be easily changed to meet varying specifications of different configurations of wheel and brake assemblies.
In accordance with another aspect of the invention it is an object to provide a torque tube which may be machined to meet varying disk brake assembly criteria, which torque tube may be machined to reduce weight and provide enhanced thermal cooling while maintaining structural stiffness and integrity.
According to still another aspect of the invention it is an object to provide a torque tube for aircraft disk brake applications wherein backplate flange stiffening may be varied to meet and/or exceed fatigue life requirements imposed on these type applications.
In accordance with a further aspect of the present invention it is an object to provide a torque tube structure which comprises axially and longitudinally oriented key surfaces which may be machined in conjunction with backplate flange stiffening ribs while varying both the configurations and dimensions of either or both the keys and/or the ribs, the ribs being varied in either their axial width dimension and/or their transverse width dimension by merely changing angular relationships which define the ribs.